1. Field of the Invention
The present invention relates to an alarm system including a master alarm device and at least one slave alarm device which are capable of communication with each other.
2. Description of the Related Art
There is provided an alarm device for detecting heat or smoke that is generated in a room or the like and issuing an alarm. Further, there is provided an alarm system including each of such alarm devices provided in respective rooms, in which one of the plurality of alarm devices and others thereof operate as a master unit and slave units, respectively, and perform the alarm operation in synchronization with one another.
As a slave unit used in such an alarm system, there is proposed “a wireless slave unit used in a specified low power two-way wireless communication system including one wireless master unit and a plurality of wireless slave units, for performing two-way wireless communication with an available frequency band being one wave, the wireless slave unit including: means for transmitting a declaration message of “communication start”, which declares that communication is to be started, when the communication is started with the wireless master unit in a status where all wireless slave units including the wireless slave unit have no communication with the wireless master unit; means for receiving the declaration message of the “communication start”, which declares that the communication has been started, with regard to any one of wireless slave units excluding the wireless slave unit; means for identifying the received declaration message, and immediately shifting the wireless slave unit into a call standby status indicating that the any one of wireless slave units excluding the wireless slave unit is communicating with the wireless master unit; means for transmitting, at a time of finishing the communication with the wireless master unit, a declaration message of “communication end”, which declares that the communication with the wireless master unit is finished; means for receiving the declaration message of the “communication end”, which declares that the communication is finished, with regard to the any one of wireless slave units excluding the wireless slave unit; and means for identifying the received declaration message, and immediately canceling the call standby status” (for example, see JP 2005-294943 A (p. 4, FIG. 1)).
In an alarm system including a master unit and slave units which are capable of communication with one another, the master unit stores and manages terminal information at the time of addition, replacement, deletion, etc. of a slave unit terminal within the alarm system. At the same time, by transferring to the other slave units an information signal regarding a fire or the like, which has been transmitted from a certain slave unit, the master unit relays the signal. In this manner, the master unit and the slave units within the alarm system perform an alarm operation in synchronization with one another.
However, as the number of slave units constituting the alarm system increases, the frequency of communication performed between the master unit and the slave units increases. Along with this, the number of communication tasks to be processed by the master unit increases, which results in increased current consumption of the master unit. Accordingly, for example, in a case of a master unit powered by a battery, a battery life thereof becomes shorter. With regard to the master unit, by supplying power from an AC power supply, it is possible to operate the master unit without having any concern about the battery level. However, the location where the master unit is installed may be limited depending on the location of the power supply outlet. In addition, the master unit and the slave unit are products of different configurations, and hence a manufacturing process and an inspection process therefor become complicated, resulting in increased workload. Consequently, manufacturing cost becomes higher.
Further, if implementation of the original functions (for example, fire detection, fire alarm, etc.) is given a lower priority due to increase in amount of processing to be executed by the master unit with regard to communication processing, the master unit fails to sufficiently perform a function as the alarm device.